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2632 lines
68 KiB
2632 lines
68 KiB
package brotli
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/* Copyright 2013 Google Inc. All Rights Reserved.
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Distributed under MIT license.
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See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
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*/
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const (
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decoderResultError = 0
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decoderResultSuccess = 1
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decoderResultNeedsMoreInput = 2
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decoderResultNeedsMoreOutput = 3
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)
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/**
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* Error code for detailed logging / production debugging.
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*
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* See ::BrotliDecoderGetErrorCode and ::BROTLI_LAST_ERROR_CODE.
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*/
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const (
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decoderNoError = 0
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decoderSuccess = 1
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decoderNeedsMoreInput = 2
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decoderNeedsMoreOutput = 3
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decoderErrorFormatExuberantNibble = -1
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decoderErrorFormatReserved = -2
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decoderErrorFormatExuberantMetaNibble = -3
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decoderErrorFormatSimpleHuffmanAlphabet = -4
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decoderErrorFormatSimpleHuffmanSame = -5
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decoderErrorFormatClSpace = -6
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decoderErrorFormatHuffmanSpace = -7
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decoderErrorFormatContextMapRepeat = -8
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decoderErrorFormatBlockLength1 = -9
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decoderErrorFormatBlockLength2 = -10
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decoderErrorFormatTransform = -11
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decoderErrorFormatDictionary = -12
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decoderErrorFormatWindowBits = -13
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decoderErrorFormatPadding1 = -14
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decoderErrorFormatPadding2 = -15
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decoderErrorFormatDistance = -16
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decoderErrorDictionaryNotSet = -19
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decoderErrorInvalidArguments = -20
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decoderErrorAllocContextModes = -21
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decoderErrorAllocTreeGroups = -22
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decoderErrorAllocContextMap = -25
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decoderErrorAllocRingBuffer1 = -26
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decoderErrorAllocRingBuffer2 = -27
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decoderErrorAllocBlockTypeTrees = -30
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decoderErrorUnreachable = -31
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)
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/**
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* The value of the last error code, negative integer.
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*
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* All other error code values are in the range from ::lastErrorCode
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* to @c -1. There are also 4 other possible non-error codes @c 0 .. @c 3 in
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* ::BrotliDecoderErrorCode enumeration.
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*/
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const lastErrorCode = decoderErrorUnreachable
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/** Options to be used with ::BrotliDecoderSetParameter. */
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const (
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decoderParamDisableRingBufferReallocation = 0
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decoderParamLargeWindow = 1
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)
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const huffmanTableBits = 8
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const huffmanTableMask = 0xFF
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/* We need the slack region for the following reasons:
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- doing up to two 16-byte copies for fast backward copying
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- inserting transformed dictionary word (5 prefix + 24 base + 8 suffix) */
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const kRingBufferWriteAheadSlack uint32 = 42
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var kCodeLengthCodeOrder = [codeLengthCodes]byte{1, 2, 3, 4, 0, 5, 17, 6, 16, 7, 8, 9, 10, 11, 12, 13, 14, 15}
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/* Static prefix code for the complex code length code lengths. */
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var kCodeLengthPrefixLength = [16]byte{2, 2, 2, 3, 2, 2, 2, 4, 2, 2, 2, 3, 2, 2, 2, 4}
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var kCodeLengthPrefixValue = [16]byte{0, 4, 3, 2, 0, 4, 3, 1, 0, 4, 3, 2, 0, 4, 3, 5}
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func decoderSetParameter(state *Reader, p int, value uint32) bool {
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if state.state != stateUninited {
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return false
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}
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switch p {
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case decoderParamDisableRingBufferReallocation:
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if !(value == 0) {
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state.canny_ringbuffer_allocation = 0
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} else {
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state.canny_ringbuffer_allocation = 1
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}
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return true
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case decoderParamLargeWindow:
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state.large_window = (!(value == 0))
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return true
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default:
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return false
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}
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}
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/* Saves error code and converts it to BrotliDecoderResult. */
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func saveErrorCode(s *Reader, e int) int {
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s.error_code = int(e)
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switch e {
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case decoderSuccess:
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return decoderResultSuccess
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case decoderNeedsMoreInput:
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return decoderResultNeedsMoreInput
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case decoderNeedsMoreOutput:
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return decoderResultNeedsMoreOutput
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default:
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return decoderResultError
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}
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}
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/* Decodes WBITS by reading 1 - 7 bits, or 0x11 for "Large Window Brotli".
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Precondition: bit-reader accumulator has at least 8 bits. */
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func decodeWindowBits(s *Reader, br *bitReader) int {
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var n uint32
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var large_window bool = s.large_window
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s.large_window = false
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takeBits(br, 1, &n)
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if n == 0 {
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s.window_bits = 16
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return decoderSuccess
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}
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takeBits(br, 3, &n)
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if n != 0 {
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s.window_bits = 17 + n
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return decoderSuccess
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}
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takeBits(br, 3, &n)
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if n == 1 {
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if large_window {
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takeBits(br, 1, &n)
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if n == 1 {
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return decoderErrorFormatWindowBits
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}
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s.large_window = true
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return decoderSuccess
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} else {
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return decoderErrorFormatWindowBits
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}
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}
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if n != 0 {
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s.window_bits = 8 + n
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return decoderSuccess
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}
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s.window_bits = 17
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return decoderSuccess
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}
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/* Decodes a number in the range [0..255], by reading 1 - 11 bits. */
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func decodeVarLenUint8(s *Reader, br *bitReader, value *uint32) int {
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var bits uint32
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switch s.substate_decode_uint8 {
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case stateDecodeUint8None:
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if !safeReadBits(br, 1, &bits) {
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return decoderNeedsMoreInput
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}
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if bits == 0 {
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*value = 0
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return decoderSuccess
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}
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fallthrough
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/* Fall through. */
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case stateDecodeUint8Short:
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if !safeReadBits(br, 3, &bits) {
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s.substate_decode_uint8 = stateDecodeUint8Short
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return decoderNeedsMoreInput
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}
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if bits == 0 {
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*value = 1
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s.substate_decode_uint8 = stateDecodeUint8None
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return decoderSuccess
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}
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/* Use output value as a temporary storage. It MUST be persisted. */
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*value = bits
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fallthrough
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/* Fall through. */
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case stateDecodeUint8Long:
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if !safeReadBits(br, *value, &bits) {
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s.substate_decode_uint8 = stateDecodeUint8Long
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return decoderNeedsMoreInput
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}
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*value = (1 << *value) + bits
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s.substate_decode_uint8 = stateDecodeUint8None
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return decoderSuccess
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default:
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return decoderErrorUnreachable
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}
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}
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/* Decodes a metablock length and flags by reading 2 - 31 bits. */
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func decodeMetaBlockLength(s *Reader, br *bitReader) int {
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var bits uint32
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var i int
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for {
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switch s.substate_metablock_header {
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case stateMetablockHeaderNone:
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if !safeReadBits(br, 1, &bits) {
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return decoderNeedsMoreInput
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}
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if bits != 0 {
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s.is_last_metablock = 1
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} else {
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s.is_last_metablock = 0
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}
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s.meta_block_remaining_len = 0
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s.is_uncompressed = 0
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s.is_metadata = 0
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if s.is_last_metablock == 0 {
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s.substate_metablock_header = stateMetablockHeaderNibbles
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break
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}
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s.substate_metablock_header = stateMetablockHeaderEmpty
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fallthrough
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/* Fall through. */
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case stateMetablockHeaderEmpty:
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if !safeReadBits(br, 1, &bits) {
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return decoderNeedsMoreInput
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}
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if bits != 0 {
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s.substate_metablock_header = stateMetablockHeaderNone
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return decoderSuccess
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}
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s.substate_metablock_header = stateMetablockHeaderNibbles
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fallthrough
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/* Fall through. */
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case stateMetablockHeaderNibbles:
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if !safeReadBits(br, 2, &bits) {
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return decoderNeedsMoreInput
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}
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s.size_nibbles = uint(byte(bits + 4))
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s.loop_counter = 0
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if bits == 3 {
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s.is_metadata = 1
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s.substate_metablock_header = stateMetablockHeaderReserved
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break
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}
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s.substate_metablock_header = stateMetablockHeaderSize
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fallthrough
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/* Fall through. */
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case stateMetablockHeaderSize:
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i = s.loop_counter
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for ; i < int(s.size_nibbles); i++ {
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if !safeReadBits(br, 4, &bits) {
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s.loop_counter = i
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return decoderNeedsMoreInput
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}
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if uint(i+1) == s.size_nibbles && s.size_nibbles > 4 && bits == 0 {
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return decoderErrorFormatExuberantNibble
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}
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s.meta_block_remaining_len |= int(bits << uint(i*4))
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}
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s.substate_metablock_header = stateMetablockHeaderUncompressed
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fallthrough
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/* Fall through. */
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case stateMetablockHeaderUncompressed:
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if s.is_last_metablock == 0 {
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if !safeReadBits(br, 1, &bits) {
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return decoderNeedsMoreInput
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}
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if bits != 0 {
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s.is_uncompressed = 1
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} else {
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s.is_uncompressed = 0
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}
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}
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s.meta_block_remaining_len++
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s.substate_metablock_header = stateMetablockHeaderNone
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return decoderSuccess
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case stateMetablockHeaderReserved:
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if !safeReadBits(br, 1, &bits) {
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return decoderNeedsMoreInput
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}
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if bits != 0 {
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return decoderErrorFormatReserved
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}
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s.substate_metablock_header = stateMetablockHeaderBytes
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fallthrough
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/* Fall through. */
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case stateMetablockHeaderBytes:
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if !safeReadBits(br, 2, &bits) {
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return decoderNeedsMoreInput
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}
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if bits == 0 {
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s.substate_metablock_header = stateMetablockHeaderNone
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return decoderSuccess
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}
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s.size_nibbles = uint(byte(bits))
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s.substate_metablock_header = stateMetablockHeaderMetadata
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fallthrough
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/* Fall through. */
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case stateMetablockHeaderMetadata:
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i = s.loop_counter
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for ; i < int(s.size_nibbles); i++ {
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if !safeReadBits(br, 8, &bits) {
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s.loop_counter = i
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return decoderNeedsMoreInput
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}
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if uint(i+1) == s.size_nibbles && s.size_nibbles > 1 && bits == 0 {
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return decoderErrorFormatExuberantMetaNibble
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}
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s.meta_block_remaining_len |= int(bits << uint(i*8))
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}
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s.meta_block_remaining_len++
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s.substate_metablock_header = stateMetablockHeaderNone
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return decoderSuccess
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default:
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return decoderErrorUnreachable
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}
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}
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}
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/* Decodes the Huffman code.
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This method doesn't read data from the bit reader, BUT drops the amount of
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bits that correspond to the decoded symbol.
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bits MUST contain at least 15 (BROTLI_HUFFMAN_MAX_CODE_LENGTH) valid bits. */
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func decodeSymbol(bits uint32, table []huffmanCode, br *bitReader) uint32 {
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table = table[bits&huffmanTableMask:]
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if table[0].bits > huffmanTableBits {
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var nbits uint32 = uint32(table[0].bits) - huffmanTableBits
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dropBits(br, huffmanTableBits)
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table = table[uint32(table[0].value)+((bits>>huffmanTableBits)&bitMask(nbits)):]
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}
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dropBits(br, uint32(table[0].bits))
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return uint32(table[0].value)
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}
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/* Reads and decodes the next Huffman code from bit-stream.
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This method peeks 16 bits of input and drops 0 - 15 of them. */
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func readSymbol(table []huffmanCode, br *bitReader) uint32 {
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return decodeSymbol(get16BitsUnmasked(br), table, br)
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}
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/* Same as DecodeSymbol, but it is known that there is less than 15 bits of
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input are currently available. */
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func safeDecodeSymbol(table []huffmanCode, br *bitReader, result *uint32) bool {
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var val uint32
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var available_bits uint32 = getAvailableBits(br)
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if available_bits == 0 {
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if table[0].bits == 0 {
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*result = uint32(table[0].value)
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return true
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}
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return false /* No valid bits at all. */
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}
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val = uint32(getBitsUnmasked(br))
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table = table[val&huffmanTableMask:]
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if table[0].bits <= huffmanTableBits {
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if uint32(table[0].bits) <= available_bits {
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dropBits(br, uint32(table[0].bits))
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*result = uint32(table[0].value)
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return true
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} else {
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return false /* Not enough bits for the first level. */
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}
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}
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if available_bits <= huffmanTableBits {
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return false /* Not enough bits to move to the second level. */
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}
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/* Speculatively drop HUFFMAN_TABLE_BITS. */
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val = (val & bitMask(uint32(table[0].bits))) >> huffmanTableBits
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available_bits -= huffmanTableBits
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table = table[uint32(table[0].value)+val:]
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if available_bits < uint32(table[0].bits) {
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return false /* Not enough bits for the second level. */
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}
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dropBits(br, huffmanTableBits+uint32(table[0].bits))
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*result = uint32(table[0].value)
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return true
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}
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func safeReadSymbol(table []huffmanCode, br *bitReader, result *uint32) bool {
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var val uint32
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if safeGetBits(br, 15, &val) {
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*result = decodeSymbol(val, table, br)
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return true
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}
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return safeDecodeSymbol(table, br, result)
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}
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/* Makes a look-up in first level Huffman table. Peeks 8 bits. */
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func preloadSymbol(safe int, table []huffmanCode, br *bitReader, bits *uint32, value *uint32) {
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if safe != 0 {
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return
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}
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table = table[getBits(br, huffmanTableBits):]
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*bits = uint32(table[0].bits)
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*value = uint32(table[0].value)
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}
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/* Decodes the next Huffman code using data prepared by PreloadSymbol.
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Reads 0 - 15 bits. Also peeks 8 following bits. */
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func readPreloadedSymbol(table []huffmanCode, br *bitReader, bits *uint32, value *uint32) uint32 {
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var result uint32 = *value
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var ext []huffmanCode
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if *bits > huffmanTableBits {
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var val uint32 = get16BitsUnmasked(br)
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ext = table[val&huffmanTableMask:][*value:]
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var mask uint32 = bitMask((*bits - huffmanTableBits))
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dropBits(br, huffmanTableBits)
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ext = ext[(val>>huffmanTableBits)&mask:]
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dropBits(br, uint32(ext[0].bits))
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result = uint32(ext[0].value)
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} else {
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dropBits(br, *bits)
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}
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preloadSymbol(0, table, br, bits, value)
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return result
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}
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func log2Floor(x uint32) uint32 {
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var result uint32 = 0
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for x != 0 {
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x >>= 1
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result++
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}
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return result
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}
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/* Reads (s->symbol + 1) symbols.
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Totally 1..4 symbols are read, 1..11 bits each.
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The list of symbols MUST NOT contain duplicates. */
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func readSimpleHuffmanSymbols(alphabet_size uint32, max_symbol uint32, s *Reader) int {
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var br *bitReader = &s.br
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var max_bits uint32 = log2Floor(alphabet_size - 1)
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var i uint32 = s.sub_loop_counter
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/* max_bits == 1..11; symbol == 0..3; 1..44 bits will be read. */
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var num_symbols uint32 = s.symbol
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for i <= num_symbols {
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var v uint32
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if !safeReadBits(br, max_bits, &v) {
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s.sub_loop_counter = i
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s.substate_huffman = stateHuffmanSimpleRead
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return decoderNeedsMoreInput
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}
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if v >= max_symbol {
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return decoderErrorFormatSimpleHuffmanAlphabet
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}
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s.symbols_lists_array[i] = uint16(v)
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i++
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}
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for i = 0; i < num_symbols; i++ {
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var k uint32 = i + 1
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for ; k <= num_symbols; k++ {
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if s.symbols_lists_array[i] == s.symbols_lists_array[k] {
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return decoderErrorFormatSimpleHuffmanSame
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}
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}
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}
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return decoderSuccess
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}
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/* Process single decoded symbol code length:
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A) reset the repeat variable
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B) remember code length (if it is not 0)
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C) extend corresponding index-chain
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D) reduce the Huffman space
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E) update the histogram */
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func processSingleCodeLength(code_len uint32, symbol *uint32, repeat *uint32, space *uint32, prev_code_len *uint32, symbol_lists symbolList, code_length_histo []uint16, next_symbol []int) {
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*repeat = 0
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if code_len != 0 { /* code_len == 1..15 */
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symbolListPut(symbol_lists, next_symbol[code_len], uint16(*symbol))
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next_symbol[code_len] = int(*symbol)
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*prev_code_len = code_len
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*space -= 32768 >> code_len
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code_length_histo[code_len]++
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}
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(*symbol)++
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}
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/* Process repeated symbol code length.
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A) Check if it is the extension of previous repeat sequence; if the decoded
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value is not BROTLI_REPEAT_PREVIOUS_CODE_LENGTH, then it is a new
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symbol-skip
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B) Update repeat variable
|
|
C) Check if operation is feasible (fits alphabet)
|
|
D) For each symbol do the same operations as in ProcessSingleCodeLength
|
|
|
|
PRECONDITION: code_len == BROTLI_REPEAT_PREVIOUS_CODE_LENGTH or
|
|
code_len == BROTLI_REPEAT_ZERO_CODE_LENGTH */
|
|
func processRepeatedCodeLength(code_len uint32, repeat_delta uint32, alphabet_size uint32, symbol *uint32, repeat *uint32, space *uint32, prev_code_len *uint32, repeat_code_len *uint32, symbol_lists symbolList, code_length_histo []uint16, next_symbol []int) {
|
|
var old_repeat uint32 /* for BROTLI_REPEAT_ZERO_CODE_LENGTH */ /* for BROTLI_REPEAT_ZERO_CODE_LENGTH */
|
|
var extra_bits uint32 = 3
|
|
var new_len uint32 = 0
|
|
if code_len == repeatPreviousCodeLength {
|
|
new_len = *prev_code_len
|
|
extra_bits = 2
|
|
}
|
|
|
|
if *repeat_code_len != new_len {
|
|
*repeat = 0
|
|
*repeat_code_len = new_len
|
|
}
|
|
|
|
old_repeat = *repeat
|
|
if *repeat > 0 {
|
|
*repeat -= 2
|
|
*repeat <<= extra_bits
|
|
}
|
|
|
|
*repeat += repeat_delta + 3
|
|
repeat_delta = *repeat - old_repeat
|
|
if *symbol+repeat_delta > alphabet_size {
|
|
*symbol = alphabet_size
|
|
*space = 0xFFFFF
|
|
return
|
|
}
|
|
|
|
if *repeat_code_len != 0 {
|
|
var last uint = uint(*symbol + repeat_delta)
|
|
var next int = next_symbol[*repeat_code_len]
|
|
for {
|
|
symbolListPut(symbol_lists, next, uint16(*symbol))
|
|
next = int(*symbol)
|
|
(*symbol)++
|
|
if (*symbol) == uint32(last) {
|
|
break
|
|
}
|
|
}
|
|
|
|
next_symbol[*repeat_code_len] = next
|
|
*space -= repeat_delta << (15 - *repeat_code_len)
|
|
code_length_histo[*repeat_code_len] = uint16(uint32(code_length_histo[*repeat_code_len]) + repeat_delta)
|
|
} else {
|
|
*symbol += repeat_delta
|
|
}
|
|
}
|
|
|
|
/* Reads and decodes symbol codelengths. */
|
|
func readSymbolCodeLengths(alphabet_size uint32, s *Reader) int {
|
|
var br *bitReader = &s.br
|
|
var symbol uint32 = s.symbol
|
|
var repeat uint32 = s.repeat
|
|
var space uint32 = s.space
|
|
var prev_code_len uint32 = s.prev_code_len
|
|
var repeat_code_len uint32 = s.repeat_code_len
|
|
var symbol_lists symbolList = s.symbol_lists
|
|
var code_length_histo []uint16 = s.code_length_histo[:]
|
|
var next_symbol []int = s.next_symbol[:]
|
|
if !warmupBitReader(br) {
|
|
return decoderNeedsMoreInput
|
|
}
|
|
var p []huffmanCode
|
|
for symbol < alphabet_size && space > 0 {
|
|
p = s.table[:]
|
|
var code_len uint32
|
|
if !checkInputAmount(br, shortFillBitWindowRead) {
|
|
s.symbol = symbol
|
|
s.repeat = repeat
|
|
s.prev_code_len = prev_code_len
|
|
s.repeat_code_len = repeat_code_len
|
|
s.space = space
|
|
return decoderNeedsMoreInput
|
|
}
|
|
|
|
fillBitWindow16(br)
|
|
p = p[getBitsUnmasked(br)&uint64(bitMask(huffmanMaxCodeLengthCodeLength)):]
|
|
dropBits(br, uint32(p[0].bits)) /* Use 1..5 bits. */
|
|
code_len = uint32(p[0].value) /* code_len == 0..17 */
|
|
if code_len < repeatPreviousCodeLength {
|
|
processSingleCodeLength(code_len, &symbol, &repeat, &space, &prev_code_len, symbol_lists, code_length_histo, next_symbol) /* code_len == 16..17, extra_bits == 2..3 */
|
|
} else {
|
|
var extra_bits uint32
|
|
if code_len == repeatPreviousCodeLength {
|
|
extra_bits = 2
|
|
} else {
|
|
extra_bits = 3
|
|
}
|
|
var repeat_delta uint32 = uint32(getBitsUnmasked(br)) & bitMask(extra_bits)
|
|
dropBits(br, extra_bits)
|
|
processRepeatedCodeLength(code_len, repeat_delta, alphabet_size, &symbol, &repeat, &space, &prev_code_len, &repeat_code_len, symbol_lists, code_length_histo, next_symbol)
|
|
}
|
|
}
|
|
|
|
s.space = space
|
|
return decoderSuccess
|
|
}
|
|
|
|
func safeReadSymbolCodeLengths(alphabet_size uint32, s *Reader) int {
|
|
var br *bitReader = &s.br
|
|
var get_byte bool = false
|
|
var p []huffmanCode
|
|
for s.symbol < alphabet_size && s.space > 0 {
|
|
p = s.table[:]
|
|
var code_len uint32
|
|
var available_bits uint32
|
|
var bits uint32 = 0
|
|
if get_byte && !pullByte(br) {
|
|
return decoderNeedsMoreInput
|
|
}
|
|
get_byte = false
|
|
available_bits = getAvailableBits(br)
|
|
if available_bits != 0 {
|
|
bits = uint32(getBitsUnmasked(br))
|
|
}
|
|
|
|
p = p[bits&bitMask(huffmanMaxCodeLengthCodeLength):]
|
|
if uint32(p[0].bits) > available_bits {
|
|
get_byte = true
|
|
continue
|
|
}
|
|
|
|
code_len = uint32(p[0].value) /* code_len == 0..17 */
|
|
if code_len < repeatPreviousCodeLength {
|
|
dropBits(br, uint32(p[0].bits))
|
|
processSingleCodeLength(code_len, &s.symbol, &s.repeat, &s.space, &s.prev_code_len, s.symbol_lists, s.code_length_histo[:], s.next_symbol[:]) /* code_len == 16..17, extra_bits == 2..3 */
|
|
} else {
|
|
var extra_bits uint32 = code_len - 14
|
|
var repeat_delta uint32 = (bits >> p[0].bits) & bitMask(extra_bits)
|
|
if available_bits < uint32(p[0].bits)+extra_bits {
|
|
get_byte = true
|
|
continue
|
|
}
|
|
|
|
dropBits(br, uint32(p[0].bits)+extra_bits)
|
|
processRepeatedCodeLength(code_len, repeat_delta, alphabet_size, &s.symbol, &s.repeat, &s.space, &s.prev_code_len, &s.repeat_code_len, s.symbol_lists, s.code_length_histo[:], s.next_symbol[:])
|
|
}
|
|
}
|
|
|
|
return decoderSuccess
|
|
}
|
|
|
|
/* Reads and decodes 15..18 codes using static prefix code.
|
|
Each code is 2..4 bits long. In total 30..72 bits are used. */
|
|
func readCodeLengthCodeLengths(s *Reader) int {
|
|
var br *bitReader = &s.br
|
|
var num_codes uint32 = s.repeat
|
|
var space uint32 = s.space
|
|
var i uint32 = s.sub_loop_counter
|
|
for ; i < codeLengthCodes; i++ {
|
|
var code_len_idx byte = kCodeLengthCodeOrder[i]
|
|
var ix uint32
|
|
var v uint32
|
|
if !safeGetBits(br, 4, &ix) {
|
|
var available_bits uint32 = getAvailableBits(br)
|
|
if available_bits != 0 {
|
|
ix = uint32(getBitsUnmasked(br) & 0xF)
|
|
} else {
|
|
ix = 0
|
|
}
|
|
|
|
if uint32(kCodeLengthPrefixLength[ix]) > available_bits {
|
|
s.sub_loop_counter = i
|
|
s.repeat = num_codes
|
|
s.space = space
|
|
s.substate_huffman = stateHuffmanComplex
|
|
return decoderNeedsMoreInput
|
|
}
|
|
}
|
|
|
|
v = uint32(kCodeLengthPrefixValue[ix])
|
|
dropBits(br, uint32(kCodeLengthPrefixLength[ix]))
|
|
s.code_length_code_lengths[code_len_idx] = byte(v)
|
|
if v != 0 {
|
|
space = space - (32 >> v)
|
|
num_codes++
|
|
s.code_length_histo[v]++
|
|
if space-1 >= 32 {
|
|
/* space is 0 or wrapped around. */
|
|
break
|
|
}
|
|
}
|
|
}
|
|
|
|
if num_codes != 1 && space != 0 {
|
|
return decoderErrorFormatClSpace
|
|
}
|
|
|
|
return decoderSuccess
|
|
}
|
|
|
|
/* Decodes the Huffman tables.
|
|
There are 2 scenarios:
|
|
A) Huffman code contains only few symbols (1..4). Those symbols are read
|
|
directly; their code lengths are defined by the number of symbols.
|
|
For this scenario 4 - 49 bits will be read.
|
|
|
|
B) 2-phase decoding:
|
|
B.1) Small Huffman table is decoded; it is specified with code lengths
|
|
encoded with predefined entropy code. 32 - 74 bits are used.
|
|
B.2) Decoded table is used to decode code lengths of symbols in resulting
|
|
Huffman table. In worst case 3520 bits are read. */
|
|
func readHuffmanCode(alphabet_size uint32, max_symbol uint32, table []huffmanCode, opt_table_size *uint32, s *Reader) int {
|
|
var br *bitReader = &s.br
|
|
|
|
/* Unnecessary masking, but might be good for safety. */
|
|
alphabet_size &= 0x7FF
|
|
|
|
/* State machine. */
|
|
for {
|
|
switch s.substate_huffman {
|
|
case stateHuffmanNone:
|
|
if !safeReadBits(br, 2, &s.sub_loop_counter) {
|
|
return decoderNeedsMoreInput
|
|
}
|
|
|
|
/* The value is used as follows:
|
|
1 for simple code;
|
|
0 for no skipping, 2 skips 2 code lengths, 3 skips 3 code lengths */
|
|
if s.sub_loop_counter != 1 {
|
|
s.space = 32
|
|
s.repeat = 0 /* num_codes */
|
|
var i int
|
|
for i = 0; i <= huffmanMaxCodeLengthCodeLength; i++ {
|
|
s.code_length_histo[i] = 0
|
|
}
|
|
|
|
for i = 0; i < codeLengthCodes; i++ {
|
|
s.code_length_code_lengths[i] = 0
|
|
}
|
|
|
|
s.substate_huffman = stateHuffmanComplex
|
|
continue
|
|
}
|
|
fallthrough
|
|
|
|
/* Read symbols, codes & code lengths directly. */
|
|
case stateHuffmanSimpleSize:
|
|
if !safeReadBits(br, 2, &s.symbol) { /* num_symbols */
|
|
s.substate_huffman = stateHuffmanSimpleSize
|
|
return decoderNeedsMoreInput
|
|
}
|
|
|
|
s.sub_loop_counter = 0
|
|
fallthrough
|
|
|
|
case stateHuffmanSimpleRead:
|
|
{
|
|
var result int = readSimpleHuffmanSymbols(alphabet_size, max_symbol, s)
|
|
if result != decoderSuccess {
|
|
return result
|
|
}
|
|
}
|
|
fallthrough
|
|
|
|
case stateHuffmanSimpleBuild:
|
|
var table_size uint32
|
|
if s.symbol == 3 {
|
|
var bits uint32
|
|
if !safeReadBits(br, 1, &bits) {
|
|
s.substate_huffman = stateHuffmanSimpleBuild
|
|
return decoderNeedsMoreInput
|
|
}
|
|
|
|
s.symbol += bits
|
|
}
|
|
|
|
table_size = buildSimpleHuffmanTable(table, huffmanTableBits, s.symbols_lists_array[:], s.symbol)
|
|
if opt_table_size != nil {
|
|
*opt_table_size = table_size
|
|
}
|
|
|
|
s.substate_huffman = stateHuffmanNone
|
|
return decoderSuccess
|
|
|
|
/* Decode Huffman-coded code lengths. */
|
|
case stateHuffmanComplex:
|
|
{
|
|
var i uint32
|
|
var result int = readCodeLengthCodeLengths(s)
|
|
if result != decoderSuccess {
|
|
return result
|
|
}
|
|
|
|
buildCodeLengthsHuffmanTable(s.table[:], s.code_length_code_lengths[:], s.code_length_histo[:])
|
|
for i = 0; i < 16; i++ {
|
|
s.code_length_histo[i] = 0
|
|
}
|
|
|
|
for i = 0; i <= huffmanMaxCodeLength; i++ {
|
|
s.next_symbol[i] = int(i) - (huffmanMaxCodeLength + 1)
|
|
symbolListPut(s.symbol_lists, s.next_symbol[i], 0xFFFF)
|
|
}
|
|
|
|
s.symbol = 0
|
|
s.prev_code_len = initialRepeatedCodeLength
|
|
s.repeat = 0
|
|
s.repeat_code_len = 0
|
|
s.space = 32768
|
|
s.substate_huffman = stateHuffmanLengthSymbols
|
|
}
|
|
fallthrough
|
|
|
|
case stateHuffmanLengthSymbols:
|
|
var table_size uint32
|
|
var result int = readSymbolCodeLengths(max_symbol, s)
|
|
if result == decoderNeedsMoreInput {
|
|
result = safeReadSymbolCodeLengths(max_symbol, s)
|
|
}
|
|
|
|
if result != decoderSuccess {
|
|
return result
|
|
}
|
|
|
|
if s.space != 0 {
|
|
return decoderErrorFormatHuffmanSpace
|
|
}
|
|
|
|
table_size = buildHuffmanTable(table, huffmanTableBits, s.symbol_lists, s.code_length_histo[:])
|
|
if opt_table_size != nil {
|
|
*opt_table_size = table_size
|
|
}
|
|
|
|
s.substate_huffman = stateHuffmanNone
|
|
return decoderSuccess
|
|
|
|
default:
|
|
return decoderErrorUnreachable
|
|
}
|
|
}
|
|
}
|
|
|
|
/* Decodes a block length by reading 3..39 bits. */
|
|
func readBlockLength(table []huffmanCode, br *bitReader) uint32 {
|
|
var code uint32
|
|
var nbits uint32
|
|
code = readSymbol(table, br)
|
|
nbits = kBlockLengthPrefixCode[code].nbits /* nbits == 2..24 */
|
|
return kBlockLengthPrefixCode[code].offset + readBits(br, nbits)
|
|
}
|
|
|
|
/* WARNING: if state is not BROTLI_STATE_READ_BLOCK_LENGTH_NONE, then
|
|
reading can't be continued with ReadBlockLength. */
|
|
func safeReadBlockLength(s *Reader, result *uint32, table []huffmanCode, br *bitReader) bool {
|
|
var index uint32
|
|
if s.substate_read_block_length == stateReadBlockLengthNone {
|
|
if !safeReadSymbol(table, br, &index) {
|
|
return false
|
|
}
|
|
} else {
|
|
index = s.block_length_index
|
|
}
|
|
{
|
|
var bits uint32 /* nbits == 2..24 */
|
|
var nbits uint32 = kBlockLengthPrefixCode[index].nbits
|
|
if !safeReadBits(br, nbits, &bits) {
|
|
s.block_length_index = index
|
|
s.substate_read_block_length = stateReadBlockLengthSuffix
|
|
return false
|
|
}
|
|
|
|
*result = kBlockLengthPrefixCode[index].offset + bits
|
|
s.substate_read_block_length = stateReadBlockLengthNone
|
|
return true
|
|
}
|
|
}
|
|
|
|
/* Transform:
|
|
1) initialize list L with values 0, 1,... 255
|
|
2) For each input element X:
|
|
2.1) let Y = L[X]
|
|
2.2) remove X-th element from L
|
|
2.3) prepend Y to L
|
|
2.4) append Y to output
|
|
|
|
In most cases max(Y) <= 7, so most of L remains intact.
|
|
To reduce the cost of initialization, we reuse L, remember the upper bound
|
|
of Y values, and reinitialize only first elements in L.
|
|
|
|
Most of input values are 0 and 1. To reduce number of branches, we replace
|
|
inner for loop with do-while. */
|
|
func inverseMoveToFrontTransform(v []byte, v_len uint32, state *Reader) {
|
|
var mtf [256]byte
|
|
var i int
|
|
for i = 1; i < 256; i++ {
|
|
mtf[i] = byte(i)
|
|
}
|
|
var mtf_1 byte
|
|
|
|
/* Transform the input. */
|
|
for i = 0; uint32(i) < v_len; i++ {
|
|
var index int = int(v[i])
|
|
var value byte = mtf[index]
|
|
v[i] = value
|
|
mtf_1 = value
|
|
for index >= 1 {
|
|
index--
|
|
mtf[index+1] = mtf[index]
|
|
}
|
|
|
|
mtf[0] = mtf_1
|
|
}
|
|
}
|
|
|
|
/* Decodes a series of Huffman table using ReadHuffmanCode function. */
|
|
func huffmanTreeGroupDecode(group *huffmanTreeGroup, s *Reader) int {
|
|
if s.substate_tree_group != stateTreeGroupLoop {
|
|
s.next = group.codes
|
|
s.htree_index = 0
|
|
s.substate_tree_group = stateTreeGroupLoop
|
|
}
|
|
|
|
for s.htree_index < int(group.num_htrees) {
|
|
var table_size uint32
|
|
var result int = readHuffmanCode(uint32(group.alphabet_size), uint32(group.max_symbol), s.next, &table_size, s)
|
|
if result != decoderSuccess {
|
|
return result
|
|
}
|
|
group.htrees[s.htree_index] = s.next
|
|
s.next = s.next[table_size:]
|
|
s.htree_index++
|
|
}
|
|
|
|
s.substate_tree_group = stateTreeGroupNone
|
|
return decoderSuccess
|
|
}
|
|
|
|
/* Decodes a context map.
|
|
Decoding is done in 4 phases:
|
|
1) Read auxiliary information (6..16 bits) and allocate memory.
|
|
In case of trivial context map, decoding is finished at this phase.
|
|
2) Decode Huffman table using ReadHuffmanCode function.
|
|
This table will be used for reading context map items.
|
|
3) Read context map items; "0" values could be run-length encoded.
|
|
4) Optionally, apply InverseMoveToFront transform to the resulting map. */
|
|
func decodeContextMap(context_map_size uint32, num_htrees *uint32, context_map_arg *[]byte, s *Reader) int {
|
|
var br *bitReader = &s.br
|
|
var result int = decoderSuccess
|
|
|
|
switch int(s.substate_context_map) {
|
|
case stateContextMapNone:
|
|
result = decodeVarLenUint8(s, br, num_htrees)
|
|
if result != decoderSuccess {
|
|
return result
|
|
}
|
|
|
|
(*num_htrees)++
|
|
s.context_index = 0
|
|
*context_map_arg = make([]byte, uint(context_map_size))
|
|
if *context_map_arg == nil {
|
|
return decoderErrorAllocContextMap
|
|
}
|
|
|
|
if *num_htrees <= 1 {
|
|
for i := 0; i < int(context_map_size); i++ {
|
|
(*context_map_arg)[i] = 0
|
|
}
|
|
return decoderSuccess
|
|
}
|
|
|
|
s.substate_context_map = stateContextMapReadPrefix
|
|
fallthrough
|
|
/* Fall through. */
|
|
case stateContextMapReadPrefix:
|
|
{
|
|
var bits uint32
|
|
|
|
/* In next stage ReadHuffmanCode uses at least 4 bits, so it is safe
|
|
to peek 4 bits ahead. */
|
|
if !safeGetBits(br, 5, &bits) {
|
|
return decoderNeedsMoreInput
|
|
}
|
|
|
|
if bits&1 != 0 { /* Use RLE for zeros. */
|
|
s.max_run_length_prefix = (bits >> 1) + 1
|
|
dropBits(br, 5)
|
|
} else {
|
|
s.max_run_length_prefix = 0
|
|
dropBits(br, 1)
|
|
}
|
|
|
|
s.substate_context_map = stateContextMapHuffman
|
|
}
|
|
fallthrough
|
|
|
|
/* Fall through. */
|
|
case stateContextMapHuffman:
|
|
{
|
|
var alphabet_size uint32 = *num_htrees + s.max_run_length_prefix
|
|
result = readHuffmanCode(alphabet_size, alphabet_size, s.context_map_table[:], nil, s)
|
|
if result != decoderSuccess {
|
|
return result
|
|
}
|
|
s.code = 0xFFFF
|
|
s.substate_context_map = stateContextMapDecode
|
|
}
|
|
fallthrough
|
|
|
|
/* Fall through. */
|
|
case stateContextMapDecode:
|
|
{
|
|
var context_index uint32 = s.context_index
|
|
var max_run_length_prefix uint32 = s.max_run_length_prefix
|
|
var context_map []byte = *context_map_arg
|
|
var code uint32 = s.code
|
|
var skip_preamble bool = (code != 0xFFFF)
|
|
for context_index < context_map_size || skip_preamble {
|
|
if !skip_preamble {
|
|
if !safeReadSymbol(s.context_map_table[:], br, &code) {
|
|
s.code = 0xFFFF
|
|
s.context_index = context_index
|
|
return decoderNeedsMoreInput
|
|
}
|
|
|
|
if code == 0 {
|
|
context_map[context_index] = 0
|
|
context_index++
|
|
continue
|
|
}
|
|
|
|
if code > max_run_length_prefix {
|
|
context_map[context_index] = byte(code - max_run_length_prefix)
|
|
context_index++
|
|
continue
|
|
}
|
|
} else {
|
|
skip_preamble = false
|
|
}
|
|
|
|
/* RLE sub-stage. */
|
|
{
|
|
var reps uint32
|
|
if !safeReadBits(br, code, &reps) {
|
|
s.code = code
|
|
s.context_index = context_index
|
|
return decoderNeedsMoreInput
|
|
}
|
|
|
|
reps += 1 << code
|
|
if context_index+reps > context_map_size {
|
|
return decoderErrorFormatContextMapRepeat
|
|
}
|
|
|
|
for {
|
|
context_map[context_index] = 0
|
|
context_index++
|
|
reps--
|
|
if reps == 0 {
|
|
break
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
fallthrough
|
|
|
|
case stateContextMapTransform:
|
|
var bits uint32
|
|
if !safeReadBits(br, 1, &bits) {
|
|
s.substate_context_map = stateContextMapTransform
|
|
return decoderNeedsMoreInput
|
|
}
|
|
|
|
if bits != 0 {
|
|
inverseMoveToFrontTransform(*context_map_arg, context_map_size, s)
|
|
}
|
|
|
|
s.substate_context_map = stateContextMapNone
|
|
return decoderSuccess
|
|
|
|
default:
|
|
return decoderErrorUnreachable
|
|
}
|
|
}
|
|
|
|
/* Decodes a command or literal and updates block type ring-buffer.
|
|
Reads 3..54 bits. */
|
|
func decodeBlockTypeAndLength(safe int, s *Reader, tree_type int) bool {
|
|
var max_block_type uint32 = s.num_block_types[tree_type]
|
|
var type_tree []huffmanCode
|
|
type_tree = s.block_type_trees[tree_type*huffmanMaxSize258:]
|
|
var len_tree []huffmanCode
|
|
len_tree = s.block_len_trees[tree_type*huffmanMaxSize26:]
|
|
var br *bitReader = &s.br
|
|
var ringbuffer []uint32 = s.block_type_rb[tree_type*2:]
|
|
var block_type uint32
|
|
if max_block_type <= 1 {
|
|
return false
|
|
}
|
|
|
|
/* Read 0..15 + 3..39 bits. */
|
|
if safe == 0 {
|
|
block_type = readSymbol(type_tree, br)
|
|
s.block_length[tree_type] = readBlockLength(len_tree, br)
|
|
} else {
|
|
var memento bitReaderState
|
|
bitReaderSaveState(br, &memento)
|
|
if !safeReadSymbol(type_tree, br, &block_type) {
|
|
return false
|
|
}
|
|
if !safeReadBlockLength(s, &s.block_length[tree_type], len_tree, br) {
|
|
s.substate_read_block_length = stateReadBlockLengthNone
|
|
bitReaderRestoreState(br, &memento)
|
|
return false
|
|
}
|
|
}
|
|
|
|
if block_type == 1 {
|
|
block_type = ringbuffer[1] + 1
|
|
} else if block_type == 0 {
|
|
block_type = ringbuffer[0]
|
|
} else {
|
|
block_type -= 2
|
|
}
|
|
|
|
if block_type >= max_block_type {
|
|
block_type -= max_block_type
|
|
}
|
|
|
|
ringbuffer[0] = ringbuffer[1]
|
|
ringbuffer[1] = block_type
|
|
return true
|
|
}
|
|
|
|
func detectTrivialLiteralBlockTypes(s *Reader) {
|
|
var i uint
|
|
for i = 0; i < 8; i++ {
|
|
s.trivial_literal_contexts[i] = 0
|
|
}
|
|
for i = 0; uint32(i) < s.num_block_types[0]; i++ {
|
|
var offset uint = i << literalContextBits
|
|
var error uint = 0
|
|
var sample uint = uint(s.context_map[offset])
|
|
var j uint
|
|
for j = 0; j < 1<<literalContextBits; {
|
|
var k int
|
|
for k = 0; k < 4; k++ {
|
|
error |= uint(s.context_map[offset+j]) ^ sample
|
|
j++
|
|
}
|
|
}
|
|
|
|
if error == 0 {
|
|
s.trivial_literal_contexts[i>>5] |= 1 << (i & 31)
|
|
}
|
|
}
|
|
}
|
|
|
|
func prepareLiteralDecoding(s *Reader) {
|
|
var context_mode byte
|
|
var trivial uint
|
|
var block_type uint32 = s.block_type_rb[1]
|
|
var context_offset uint32 = block_type << literalContextBits
|
|
s.context_map_slice = s.context_map[context_offset:]
|
|
trivial = uint(s.trivial_literal_contexts[block_type>>5])
|
|
s.trivial_literal_context = int((trivial >> (block_type & 31)) & 1)
|
|
s.literal_htree = []huffmanCode(s.literal_hgroup.htrees[s.context_map_slice[0]])
|
|
context_mode = s.context_modes[block_type] & 3
|
|
s.context_lookup = getContextLUT(int(context_mode))
|
|
}
|
|
|
|
/* Decodes the block type and updates the state for literal context.
|
|
Reads 3..54 bits. */
|
|
func decodeLiteralBlockSwitchInternal(safe int, s *Reader) bool {
|
|
if !decodeBlockTypeAndLength(safe, s, 0) {
|
|
return false
|
|
}
|
|
|
|
prepareLiteralDecoding(s)
|
|
return true
|
|
}
|
|
|
|
func decodeLiteralBlockSwitch(s *Reader) {
|
|
decodeLiteralBlockSwitchInternal(0, s)
|
|
}
|
|
|
|
func safeDecodeLiteralBlockSwitch(s *Reader) bool {
|
|
return decodeLiteralBlockSwitchInternal(1, s)
|
|
}
|
|
|
|
/* Block switch for insert/copy length.
|
|
Reads 3..54 bits. */
|
|
func decodeCommandBlockSwitchInternal(safe int, s *Reader) bool {
|
|
if !decodeBlockTypeAndLength(safe, s, 1) {
|
|
return false
|
|
}
|
|
|
|
s.htree_command = []huffmanCode(s.insert_copy_hgroup.htrees[s.block_type_rb[3]])
|
|
return true
|
|
}
|
|
|
|
func decodeCommandBlockSwitch(s *Reader) {
|
|
decodeCommandBlockSwitchInternal(0, s)
|
|
}
|
|
|
|
func safeDecodeCommandBlockSwitch(s *Reader) bool {
|
|
return decodeCommandBlockSwitchInternal(1, s)
|
|
}
|
|
|
|
/* Block switch for distance codes.
|
|
Reads 3..54 bits. */
|
|
func decodeDistanceBlockSwitchInternal(safe int, s *Reader) bool {
|
|
if !decodeBlockTypeAndLength(safe, s, 2) {
|
|
return false
|
|
}
|
|
|
|
s.dist_context_map_slice = s.dist_context_map[s.block_type_rb[5]<<distanceContextBits:]
|
|
s.dist_htree_index = s.dist_context_map_slice[s.distance_context]
|
|
return true
|
|
}
|
|
|
|
func decodeDistanceBlockSwitch(s *Reader) {
|
|
decodeDistanceBlockSwitchInternal(0, s)
|
|
}
|
|
|
|
func safeDecodeDistanceBlockSwitch(s *Reader) bool {
|
|
return decodeDistanceBlockSwitchInternal(1, s)
|
|
}
|
|
|
|
func unwrittenBytes(s *Reader, wrap bool) uint {
|
|
var pos uint
|
|
if wrap && s.pos > s.ringbuffer_size {
|
|
pos = uint(s.ringbuffer_size)
|
|
} else {
|
|
pos = uint(s.pos)
|
|
}
|
|
var partial_pos_rb uint = (s.rb_roundtrips * uint(s.ringbuffer_size)) + pos
|
|
return partial_pos_rb - s.partial_pos_out
|
|
}
|
|
|
|
/* Dumps output.
|
|
Returns BROTLI_DECODER_NEEDS_MORE_OUTPUT only if there is more output to push
|
|
and either ring-buffer is as big as window size, or |force| is true. */
|
|
func writeRingBuffer(s *Reader, available_out *uint, next_out *[]byte, total_out *uint, force bool) int {
|
|
var start []byte
|
|
start = s.ringbuffer[s.partial_pos_out&uint(s.ringbuffer_mask):]
|
|
var to_write uint = unwrittenBytes(s, true)
|
|
var num_written uint = *available_out
|
|
if num_written > to_write {
|
|
num_written = to_write
|
|
}
|
|
|
|
if s.meta_block_remaining_len < 0 {
|
|
return decoderErrorFormatBlockLength1
|
|
}
|
|
|
|
if next_out != nil && *next_out == nil {
|
|
*next_out = start
|
|
} else {
|
|
if next_out != nil {
|
|
copy(*next_out, start[:num_written])
|
|
*next_out = (*next_out)[num_written:]
|
|
}
|
|
}
|
|
|
|
*available_out -= num_written
|
|
s.partial_pos_out += num_written
|
|
if total_out != nil {
|
|
*total_out = s.partial_pos_out
|
|
}
|
|
|
|
if num_written < to_write {
|
|
if s.ringbuffer_size == 1<<s.window_bits || force {
|
|
return decoderNeedsMoreOutput
|
|
} else {
|
|
return decoderSuccess
|
|
}
|
|
}
|
|
|
|
/* Wrap ring buffer only if it has reached its maximal size. */
|
|
if s.ringbuffer_size == 1<<s.window_bits && s.pos >= s.ringbuffer_size {
|
|
s.pos -= s.ringbuffer_size
|
|
s.rb_roundtrips++
|
|
if uint(s.pos) != 0 {
|
|
s.should_wrap_ringbuffer = 1
|
|
} else {
|
|
s.should_wrap_ringbuffer = 0
|
|
}
|
|
}
|
|
|
|
return decoderSuccess
|
|
}
|
|
|
|
func wrapRingBuffer(s *Reader) {
|
|
if s.should_wrap_ringbuffer != 0 {
|
|
copy(s.ringbuffer, s.ringbuffer_end[:uint(s.pos)])
|
|
s.should_wrap_ringbuffer = 0
|
|
}
|
|
}
|
|
|
|
/* Allocates ring-buffer.
|
|
|
|
s->ringbuffer_size MUST be updated by BrotliCalculateRingBufferSize before
|
|
this function is called.
|
|
|
|
Last two bytes of ring-buffer are initialized to 0, so context calculation
|
|
could be done uniformly for the first two and all other positions. */
|
|
func ensureRingBuffer(s *Reader) bool {
|
|
var old_ringbuffer []byte = s.ringbuffer
|
|
if s.ringbuffer_size == s.new_ringbuffer_size {
|
|
return true
|
|
}
|
|
|
|
s.ringbuffer = make([]byte, uint(s.new_ringbuffer_size)+uint(kRingBufferWriteAheadSlack))
|
|
if s.ringbuffer == nil {
|
|
/* Restore previous value. */
|
|
s.ringbuffer = old_ringbuffer
|
|
|
|
return false
|
|
}
|
|
|
|
s.ringbuffer[s.new_ringbuffer_size-2] = 0
|
|
s.ringbuffer[s.new_ringbuffer_size-1] = 0
|
|
|
|
if !(old_ringbuffer == nil) {
|
|
copy(s.ringbuffer, old_ringbuffer[:uint(s.pos)])
|
|
|
|
old_ringbuffer = nil
|
|
}
|
|
|
|
s.ringbuffer_size = s.new_ringbuffer_size
|
|
s.ringbuffer_mask = s.new_ringbuffer_size - 1
|
|
s.ringbuffer_end = s.ringbuffer[s.ringbuffer_size:]
|
|
|
|
return true
|
|
}
|
|
|
|
func copyUncompressedBlockToOutput(available_out *uint, next_out *[]byte, total_out *uint, s *Reader) int {
|
|
/* TODO: avoid allocation for single uncompressed block. */
|
|
if !ensureRingBuffer(s) {
|
|
return decoderErrorAllocRingBuffer1
|
|
}
|
|
|
|
/* State machine */
|
|
for {
|
|
switch s.substate_uncompressed {
|
|
case stateUncompressedNone:
|
|
{
|
|
var nbytes int = int(getRemainingBytes(&s.br))
|
|
if nbytes > s.meta_block_remaining_len {
|
|
nbytes = s.meta_block_remaining_len
|
|
}
|
|
|
|
if s.pos+nbytes > s.ringbuffer_size {
|
|
nbytes = s.ringbuffer_size - s.pos
|
|
}
|
|
|
|
/* Copy remaining bytes from s->br.buf_ to ring-buffer. */
|
|
copyBytes(s.ringbuffer[s.pos:], &s.br, uint(nbytes))
|
|
|
|
s.pos += nbytes
|
|
s.meta_block_remaining_len -= nbytes
|
|
if s.pos < 1<<s.window_bits {
|
|
if s.meta_block_remaining_len == 0 {
|
|
return decoderSuccess
|
|
}
|
|
|
|
return decoderNeedsMoreInput
|
|
}
|
|
|
|
s.substate_uncompressed = stateUncompressedWrite
|
|
}
|
|
fallthrough
|
|
|
|
case stateUncompressedWrite:
|
|
{
|
|
var result int
|
|
result = writeRingBuffer(s, available_out, next_out, total_out, false)
|
|
if result != decoderSuccess {
|
|
return result
|
|
}
|
|
|
|
if s.ringbuffer_size == 1<<s.window_bits {
|
|
s.max_distance = s.max_backward_distance
|
|
}
|
|
|
|
s.substate_uncompressed = stateUncompressedNone
|
|
break
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
/* Calculates the smallest feasible ring buffer.
|
|
|
|
If we know the data size is small, do not allocate more ring buffer
|
|
size than needed to reduce memory usage.
|
|
|
|
When this method is called, metablock size and flags MUST be decoded. */
|
|
func calculateRingBufferSize(s *Reader) {
|
|
var window_size int = 1 << s.window_bits
|
|
var new_ringbuffer_size int = window_size
|
|
var min_size int
|
|
/* We need at least 2 bytes of ring buffer size to get the last two
|
|
bytes for context from there */
|
|
if s.ringbuffer_size != 0 {
|
|
min_size = s.ringbuffer_size
|
|
} else {
|
|
min_size = 1024
|
|
}
|
|
var output_size int
|
|
|
|
/* If maximum is already reached, no further extension is retired. */
|
|
if s.ringbuffer_size == window_size {
|
|
return
|
|
}
|
|
|
|
/* Metadata blocks does not touch ring buffer. */
|
|
if s.is_metadata != 0 {
|
|
return
|
|
}
|
|
|
|
if s.ringbuffer == nil {
|
|
output_size = 0
|
|
} else {
|
|
output_size = s.pos
|
|
}
|
|
|
|
output_size += s.meta_block_remaining_len
|
|
if min_size < output_size {
|
|
min_size = output_size
|
|
}
|
|
|
|
if !(s.canny_ringbuffer_allocation == 0) {
|
|
/* Reduce ring buffer size to save memory when server is unscrupulous.
|
|
In worst case memory usage might be 1.5x bigger for a short period of
|
|
ring buffer reallocation. */
|
|
for new_ringbuffer_size>>1 >= min_size {
|
|
new_ringbuffer_size >>= 1
|
|
}
|
|
}
|
|
|
|
s.new_ringbuffer_size = new_ringbuffer_size
|
|
}
|
|
|
|
/* Reads 1..256 2-bit context modes. */
|
|
func readContextModes(s *Reader) int {
|
|
var br *bitReader = &s.br
|
|
var i int = s.loop_counter
|
|
|
|
for i < int(s.num_block_types[0]) {
|
|
var bits uint32
|
|
if !safeReadBits(br, 2, &bits) {
|
|
s.loop_counter = i
|
|
return decoderNeedsMoreInput
|
|
}
|
|
|
|
s.context_modes[i] = byte(bits)
|
|
i++
|
|
}
|
|
|
|
return decoderSuccess
|
|
}
|
|
|
|
func takeDistanceFromRingBuffer(s *Reader) {
|
|
if s.distance_code == 0 {
|
|
s.dist_rb_idx--
|
|
s.distance_code = s.dist_rb[s.dist_rb_idx&3]
|
|
|
|
/* Compensate double distance-ring-buffer roll for dictionary items. */
|
|
s.distance_context = 1
|
|
} else {
|
|
var distance_code int = s.distance_code << 1
|
|
const kDistanceShortCodeIndexOffset uint32 = 0xAAAFFF1B
|
|
const kDistanceShortCodeValueOffset uint32 = 0xFA5FA500
|
|
var v int = (s.dist_rb_idx + int(kDistanceShortCodeIndexOffset>>uint(distance_code))) & 0x3
|
|
/* kDistanceShortCodeIndexOffset has 2-bit values from LSB:
|
|
3, 2, 1, 0, 3, 3, 3, 3, 3, 3, 2, 2, 2, 2, 2, 2 */
|
|
|
|
/* kDistanceShortCodeValueOffset has 2-bit values from LSB:
|
|
-0, 0,-0, 0,-1, 1,-2, 2,-3, 3,-1, 1,-2, 2,-3, 3 */
|
|
s.distance_code = s.dist_rb[v]
|
|
|
|
v = int(kDistanceShortCodeValueOffset>>uint(distance_code)) & 0x3
|
|
if distance_code&0x3 != 0 {
|
|
s.distance_code += v
|
|
} else {
|
|
s.distance_code -= v
|
|
if s.distance_code <= 0 {
|
|
/* A huge distance will cause a () soon.
|
|
This is a little faster than failing here. */
|
|
s.distance_code = 0x7FFFFFFF
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
func safeReadBitsMaybeZero(br *bitReader, n_bits uint32, val *uint32) bool {
|
|
if n_bits != 0 {
|
|
return safeReadBits(br, n_bits, val)
|
|
} else {
|
|
*val = 0
|
|
return true
|
|
}
|
|
}
|
|
|
|
/* Precondition: s->distance_code < 0. */
|
|
func readDistanceInternal(safe int, s *Reader, br *bitReader) bool {
|
|
var distval int
|
|
var memento bitReaderState
|
|
var distance_tree []huffmanCode = []huffmanCode(s.distance_hgroup.htrees[s.dist_htree_index])
|
|
if safe == 0 {
|
|
s.distance_code = int(readSymbol(distance_tree, br))
|
|
} else {
|
|
var code uint32
|
|
bitReaderSaveState(br, &memento)
|
|
if !safeReadSymbol(distance_tree, br, &code) {
|
|
return false
|
|
}
|
|
|
|
s.distance_code = int(code)
|
|
}
|
|
|
|
/* Convert the distance code to the actual distance by possibly
|
|
looking up past distances from the s->ringbuffer. */
|
|
s.distance_context = 0
|
|
|
|
if s.distance_code&^0xF == 0 {
|
|
takeDistanceFromRingBuffer(s)
|
|
s.block_length[2]--
|
|
return true
|
|
}
|
|
|
|
distval = s.distance_code - int(s.num_direct_distance_codes)
|
|
if distval >= 0 {
|
|
var nbits uint32
|
|
var postfix int
|
|
var offset int
|
|
if safe == 0 && (s.distance_postfix_bits == 0) {
|
|
nbits = (uint32(distval) >> 1) + 1
|
|
offset = ((2 + (distval & 1)) << nbits) - 4
|
|
s.distance_code = int(s.num_direct_distance_codes) + offset + int(readBits(br, nbits))
|
|
} else {
|
|
/* This branch also works well when s->distance_postfix_bits == 0. */
|
|
var bits uint32
|
|
postfix = distval & s.distance_postfix_mask
|
|
distval >>= s.distance_postfix_bits
|
|
nbits = (uint32(distval) >> 1) + 1
|
|
if safe != 0 {
|
|
if !safeReadBitsMaybeZero(br, nbits, &bits) {
|
|
s.distance_code = -1 /* Restore precondition. */
|
|
bitReaderRestoreState(br, &memento)
|
|
return false
|
|
}
|
|
} else {
|
|
bits = readBits(br, nbits)
|
|
}
|
|
|
|
offset = ((2 + (distval & 1)) << nbits) - 4
|
|
s.distance_code = int(s.num_direct_distance_codes) + ((offset + int(bits)) << s.distance_postfix_bits) + postfix
|
|
}
|
|
}
|
|
|
|
s.distance_code = s.distance_code - numDistanceShortCodes + 1
|
|
s.block_length[2]--
|
|
return true
|
|
}
|
|
|
|
func readDistance(s *Reader, br *bitReader) {
|
|
readDistanceInternal(0, s, br)
|
|
}
|
|
|
|
func safeReadDistance(s *Reader, br *bitReader) bool {
|
|
return readDistanceInternal(1, s, br)
|
|
}
|
|
|
|
func readCommandInternal(safe int, s *Reader, br *bitReader, insert_length *int) bool {
|
|
var cmd_code uint32
|
|
var insert_len_extra uint32 = 0
|
|
var copy_length uint32
|
|
var v cmdLutElement
|
|
var memento bitReaderState
|
|
if safe == 0 {
|
|
cmd_code = readSymbol(s.htree_command, br)
|
|
} else {
|
|
bitReaderSaveState(br, &memento)
|
|
if !safeReadSymbol(s.htree_command, br, &cmd_code) {
|
|
return false
|
|
}
|
|
}
|
|
|
|
v = kCmdLut[cmd_code]
|
|
s.distance_code = int(v.distance_code)
|
|
s.distance_context = int(v.context)
|
|
s.dist_htree_index = s.dist_context_map_slice[s.distance_context]
|
|
*insert_length = int(v.insert_len_offset)
|
|
if safe == 0 {
|
|
if v.insert_len_extra_bits != 0 {
|
|
insert_len_extra = readBits(br, uint32(v.insert_len_extra_bits))
|
|
}
|
|
|
|
copy_length = readBits(br, uint32(v.copy_len_extra_bits))
|
|
} else {
|
|
if !safeReadBitsMaybeZero(br, uint32(v.insert_len_extra_bits), &insert_len_extra) || !safeReadBitsMaybeZero(br, uint32(v.copy_len_extra_bits), ©_length) {
|
|
bitReaderRestoreState(br, &memento)
|
|
return false
|
|
}
|
|
}
|
|
|
|
s.copy_length = int(copy_length) + int(v.copy_len_offset)
|
|
s.block_length[1]--
|
|
*insert_length += int(insert_len_extra)
|
|
return true
|
|
}
|
|
|
|
func readCommand(s *Reader, br *bitReader, insert_length *int) {
|
|
readCommandInternal(0, s, br, insert_length)
|
|
}
|
|
|
|
func safeReadCommand(s *Reader, br *bitReader, insert_length *int) bool {
|
|
return readCommandInternal(1, s, br, insert_length)
|
|
}
|
|
|
|
func checkInputAmountMaybeSafe(safe int, br *bitReader, num uint) bool {
|
|
if safe != 0 {
|
|
return true
|
|
}
|
|
|
|
return checkInputAmount(br, num)
|
|
}
|
|
|
|
func processCommandsInternal(safe int, s *Reader) int {
|
|
var pos int = s.pos
|
|
var i int = s.loop_counter
|
|
var result int = decoderSuccess
|
|
var br *bitReader = &s.br
|
|
var hc []huffmanCode
|
|
|
|
if !checkInputAmountMaybeSafe(safe, br, 28) {
|
|
result = decoderNeedsMoreInput
|
|
goto saveStateAndReturn
|
|
}
|
|
|
|
if safe == 0 {
|
|
warmupBitReader(br)
|
|
}
|
|
|
|
/* Jump into state machine. */
|
|
if s.state == stateCommandBegin {
|
|
goto CommandBegin
|
|
} else if s.state == stateCommandInner {
|
|
goto CommandInner
|
|
} else if s.state == stateCommandPostDecodeLiterals {
|
|
goto CommandPostDecodeLiterals
|
|
} else if s.state == stateCommandPostWrapCopy {
|
|
goto CommandPostWrapCopy
|
|
} else {
|
|
return decoderErrorUnreachable
|
|
}
|
|
|
|
CommandBegin:
|
|
if safe != 0 {
|
|
s.state = stateCommandBegin
|
|
}
|
|
|
|
if !checkInputAmountMaybeSafe(safe, br, 28) { /* 156 bits + 7 bytes */
|
|
s.state = stateCommandBegin
|
|
result = decoderNeedsMoreInput
|
|
goto saveStateAndReturn
|
|
}
|
|
|
|
if s.block_length[1] == 0 {
|
|
if safe != 0 {
|
|
if !safeDecodeCommandBlockSwitch(s) {
|
|
result = decoderNeedsMoreInput
|
|
goto saveStateAndReturn
|
|
}
|
|
} else {
|
|
decodeCommandBlockSwitch(s)
|
|
}
|
|
|
|
goto CommandBegin
|
|
}
|
|
|
|
/* Read the insert/copy length in the command. */
|
|
if safe != 0 {
|
|
if !safeReadCommand(s, br, &i) {
|
|
result = decoderNeedsMoreInput
|
|
goto saveStateAndReturn
|
|
}
|
|
} else {
|
|
readCommand(s, br, &i)
|
|
}
|
|
|
|
if i == 0 {
|
|
goto CommandPostDecodeLiterals
|
|
}
|
|
|
|
s.meta_block_remaining_len -= i
|
|
|
|
CommandInner:
|
|
if safe != 0 {
|
|
s.state = stateCommandInner
|
|
}
|
|
|
|
/* Read the literals in the command. */
|
|
if s.trivial_literal_context != 0 {
|
|
var bits uint32
|
|
var value uint32
|
|
preloadSymbol(safe, s.literal_htree, br, &bits, &value)
|
|
for {
|
|
if !checkInputAmountMaybeSafe(safe, br, 28) { /* 162 bits + 7 bytes */
|
|
s.state = stateCommandInner
|
|
result = decoderNeedsMoreInput
|
|
goto saveStateAndReturn
|
|
}
|
|
|
|
if s.block_length[0] == 0 {
|
|
if safe != 0 {
|
|
if !safeDecodeLiteralBlockSwitch(s) {
|
|
result = decoderNeedsMoreInput
|
|
goto saveStateAndReturn
|
|
}
|
|
} else {
|
|
decodeLiteralBlockSwitch(s)
|
|
}
|
|
|
|
preloadSymbol(safe, s.literal_htree, br, &bits, &value)
|
|
if s.trivial_literal_context == 0 {
|
|
goto CommandInner
|
|
}
|
|
}
|
|
|
|
if safe == 0 {
|
|
s.ringbuffer[pos] = byte(readPreloadedSymbol(s.literal_htree, br, &bits, &value))
|
|
} else {
|
|
var literal uint32
|
|
if !safeReadSymbol(s.literal_htree, br, &literal) {
|
|
result = decoderNeedsMoreInput
|
|
goto saveStateAndReturn
|
|
}
|
|
|
|
s.ringbuffer[pos] = byte(literal)
|
|
}
|
|
|
|
s.block_length[0]--
|
|
pos++
|
|
if pos == s.ringbuffer_size {
|
|
s.state = stateCommandInnerWrite
|
|
i--
|
|
goto saveStateAndReturn
|
|
}
|
|
i--
|
|
if i == 0 {
|
|
break
|
|
}
|
|
}
|
|
} else {
|
|
var p1 byte = s.ringbuffer[(pos-1)&s.ringbuffer_mask]
|
|
var p2 byte = s.ringbuffer[(pos-2)&s.ringbuffer_mask]
|
|
for {
|
|
var context byte
|
|
if !checkInputAmountMaybeSafe(safe, br, 28) { /* 162 bits + 7 bytes */
|
|
s.state = stateCommandInner
|
|
result = decoderNeedsMoreInput
|
|
goto saveStateAndReturn
|
|
}
|
|
|
|
if s.block_length[0] == 0 {
|
|
if safe != 0 {
|
|
if !safeDecodeLiteralBlockSwitch(s) {
|
|
result = decoderNeedsMoreInput
|
|
goto saveStateAndReturn
|
|
}
|
|
} else {
|
|
decodeLiteralBlockSwitch(s)
|
|
}
|
|
|
|
if s.trivial_literal_context != 0 {
|
|
goto CommandInner
|
|
}
|
|
}
|
|
|
|
context = getContext(p1, p2, s.context_lookup)
|
|
hc = []huffmanCode(s.literal_hgroup.htrees[s.context_map_slice[context]])
|
|
p2 = p1
|
|
if safe == 0 {
|
|
p1 = byte(readSymbol(hc, br))
|
|
} else {
|
|
var literal uint32
|
|
if !safeReadSymbol(hc, br, &literal) {
|
|
result = decoderNeedsMoreInput
|
|
goto saveStateAndReturn
|
|
}
|
|
|
|
p1 = byte(literal)
|
|
}
|
|
|
|
s.ringbuffer[pos] = p1
|
|
s.block_length[0]--
|
|
pos++
|
|
if pos == s.ringbuffer_size {
|
|
s.state = stateCommandInnerWrite
|
|
i--
|
|
goto saveStateAndReturn
|
|
}
|
|
i--
|
|
if i == 0 {
|
|
break
|
|
}
|
|
}
|
|
}
|
|
|
|
if s.meta_block_remaining_len <= 0 {
|
|
s.state = stateMetablockDone
|
|
goto saveStateAndReturn
|
|
}
|
|
|
|
CommandPostDecodeLiterals:
|
|
if safe != 0 {
|
|
s.state = stateCommandPostDecodeLiterals
|
|
}
|
|
|
|
if s.distance_code >= 0 {
|
|
/* Implicit distance case. */
|
|
if s.distance_code != 0 {
|
|
s.distance_context = 0
|
|
} else {
|
|
s.distance_context = 1
|
|
}
|
|
|
|
s.dist_rb_idx--
|
|
s.distance_code = s.dist_rb[s.dist_rb_idx&3]
|
|
} else {
|
|
/* Read distance code in the command, unless it was implicitly zero. */
|
|
if s.block_length[2] == 0 {
|
|
if safe != 0 {
|
|
if !safeDecodeDistanceBlockSwitch(s) {
|
|
result = decoderNeedsMoreInput
|
|
goto saveStateAndReturn
|
|
}
|
|
} else {
|
|
decodeDistanceBlockSwitch(s)
|
|
}
|
|
}
|
|
|
|
if safe != 0 {
|
|
if !safeReadDistance(s, br) {
|
|
result = decoderNeedsMoreInput
|
|
goto saveStateAndReturn
|
|
}
|
|
} else {
|
|
readDistance(s, br)
|
|
}
|
|
}
|
|
|
|
if s.max_distance != s.max_backward_distance {
|
|
if pos < s.max_backward_distance {
|
|
s.max_distance = pos
|
|
} else {
|
|
s.max_distance = s.max_backward_distance
|
|
}
|
|
}
|
|
|
|
i = s.copy_length
|
|
|
|
/* Apply copy of LZ77 back-reference, or static dictionary reference if
|
|
the distance is larger than the max LZ77 distance */
|
|
if s.distance_code > s.max_distance {
|
|
/* The maximum allowed distance is BROTLI_MAX_ALLOWED_DISTANCE = 0x7FFFFFFC.
|
|
With this choice, no signed overflow can occur after decoding
|
|
a special distance code (e.g., after adding 3 to the last distance). */
|
|
if s.distance_code > maxAllowedDistance {
|
|
return decoderErrorFormatDistance
|
|
}
|
|
|
|
if i >= minDictionaryWordLength && i <= maxDictionaryWordLength {
|
|
var address int = s.distance_code - s.max_distance - 1
|
|
var words *dictionary = s.dictionary
|
|
var trans *transforms = s.transforms
|
|
var offset int = int(s.dictionary.offsets_by_length[i])
|
|
var shift uint32 = uint32(s.dictionary.size_bits_by_length[i])
|
|
var mask int = int(bitMask(shift))
|
|
var word_idx int = address & mask
|
|
var transform_idx int = address >> shift
|
|
|
|
/* Compensate double distance-ring-buffer roll. */
|
|
s.dist_rb_idx += s.distance_context
|
|
|
|
offset += word_idx * i
|
|
if words.data == nil {
|
|
return decoderErrorDictionaryNotSet
|
|
}
|
|
|
|
if transform_idx < int(trans.num_transforms) {
|
|
var word []byte
|
|
word = words.data[offset:]
|
|
var len int = i
|
|
if transform_idx == int(trans.cutOffTransforms[0]) {
|
|
copy(s.ringbuffer[pos:], word[:uint(len)])
|
|
} else {
|
|
len = transformDictionaryWord(s.ringbuffer[pos:], word, int(len), trans, transform_idx)
|
|
}
|
|
|
|
pos += int(len)
|
|
s.meta_block_remaining_len -= int(len)
|
|
if pos >= s.ringbuffer_size {
|
|
s.state = stateCommandPostWrite1
|
|
goto saveStateAndReturn
|
|
}
|
|
} else {
|
|
return decoderErrorFormatTransform
|
|
}
|
|
} else {
|
|
return decoderErrorFormatDictionary
|
|
}
|
|
} else {
|
|
var src_start int = (pos - s.distance_code) & s.ringbuffer_mask
|
|
var copy_dst []byte
|
|
copy_dst = s.ringbuffer[pos:]
|
|
var copy_src []byte
|
|
copy_src = s.ringbuffer[src_start:]
|
|
var dst_end int = pos + i
|
|
var src_end int = src_start + i
|
|
|
|
/* Update the recent distances cache. */
|
|
s.dist_rb[s.dist_rb_idx&3] = s.distance_code
|
|
|
|
s.dist_rb_idx++
|
|
s.meta_block_remaining_len -= i
|
|
|
|
/* There are 32+ bytes of slack in the ring-buffer allocation.
|
|
Also, we have 16 short codes, that make these 16 bytes irrelevant
|
|
in the ring-buffer. Let's copy over them as a first guess. */
|
|
copy(copy_dst, copy_src[:16])
|
|
|
|
if src_end > pos && dst_end > src_start {
|
|
/* Regions intersect. */
|
|
goto CommandPostWrapCopy
|
|
}
|
|
|
|
if dst_end >= s.ringbuffer_size || src_end >= s.ringbuffer_size {
|
|
/* At least one region wraps. */
|
|
goto CommandPostWrapCopy
|
|
}
|
|
|
|
pos += i
|
|
if i > 16 {
|
|
if i > 32 {
|
|
copy(copy_dst[16:], copy_src[16:][:uint(i-16)])
|
|
} else {
|
|
/* This branch covers about 45% cases.
|
|
Fixed size short copy allows more compiler optimizations. */
|
|
copy(copy_dst[16:], copy_src[16:][:16])
|
|
}
|
|
}
|
|
}
|
|
|
|
if s.meta_block_remaining_len <= 0 {
|
|
/* Next metablock, if any. */
|
|
s.state = stateMetablockDone
|
|
|
|
goto saveStateAndReturn
|
|
} else {
|
|
goto CommandBegin
|
|
}
|
|
CommandPostWrapCopy:
|
|
{
|
|
var wrap_guard int = s.ringbuffer_size - pos
|
|
for {
|
|
i--
|
|
if i < 0 {
|
|
break
|
|
}
|
|
s.ringbuffer[pos] = s.ringbuffer[(pos-s.distance_code)&s.ringbuffer_mask]
|
|
pos++
|
|
wrap_guard--
|
|
if wrap_guard == 0 {
|
|
s.state = stateCommandPostWrite2
|
|
goto saveStateAndReturn
|
|
}
|
|
}
|
|
}
|
|
|
|
if s.meta_block_remaining_len <= 0 {
|
|
/* Next metablock, if any. */
|
|
s.state = stateMetablockDone
|
|
|
|
goto saveStateAndReturn
|
|
} else {
|
|
goto CommandBegin
|
|
}
|
|
|
|
saveStateAndReturn:
|
|
s.pos = pos
|
|
s.loop_counter = i
|
|
return result
|
|
}
|
|
|
|
func processCommands(s *Reader) int {
|
|
return processCommandsInternal(0, s)
|
|
}
|
|
|
|
func safeProcessCommands(s *Reader) int {
|
|
return processCommandsInternal(1, s)
|
|
}
|
|
|
|
/* Returns the maximum number of distance symbols which can only represent
|
|
distances not exceeding BROTLI_MAX_ALLOWED_DISTANCE. */
|
|
|
|
var maxDistanceSymbol_bound = [maxNpostfix + 1]uint32{0, 4, 12, 28}
|
|
var maxDistanceSymbol_diff = [maxNpostfix + 1]uint32{73, 126, 228, 424}
|
|
|
|
func maxDistanceSymbol(ndirect uint32, npostfix uint32) uint32 {
|
|
var postfix uint32 = 1 << npostfix
|
|
if ndirect < maxDistanceSymbol_bound[npostfix] {
|
|
return ndirect + maxDistanceSymbol_diff[npostfix] + postfix
|
|
} else if ndirect > maxDistanceSymbol_bound[npostfix]+postfix {
|
|
return ndirect + maxDistanceSymbol_diff[npostfix]
|
|
} else {
|
|
return maxDistanceSymbol_bound[npostfix] + maxDistanceSymbol_diff[npostfix] + postfix
|
|
}
|
|
}
|
|
|
|
/* Invariant: input stream is never overconsumed:
|
|
- invalid input implies that the whole stream is invalid -> any amount of
|
|
input could be read and discarded
|
|
- when result is "needs more input", then at least one more byte is REQUIRED
|
|
to complete decoding; all input data MUST be consumed by decoder, so
|
|
client could swap the input buffer
|
|
- when result is "needs more output" decoder MUST ensure that it doesn't
|
|
hold more than 7 bits in bit reader; this saves client from swapping input
|
|
buffer ahead of time
|
|
- when result is "success" decoder MUST return all unused data back to input
|
|
buffer; this is possible because the invariant is held on enter */
|
|
func decoderDecompressStream(s *Reader, available_in *uint, next_in *[]byte, available_out *uint, next_out *[]byte) int {
|
|
var result int = decoderSuccess
|
|
var br *bitReader = &s.br
|
|
|
|
/* Do not try to process further in a case of unrecoverable error. */
|
|
if int(s.error_code) < 0 {
|
|
return decoderResultError
|
|
}
|
|
|
|
if *available_out != 0 && (next_out == nil || *next_out == nil) {
|
|
return saveErrorCode(s, decoderErrorInvalidArguments)
|
|
}
|
|
|
|
if *available_out == 0 {
|
|
next_out = nil
|
|
}
|
|
if s.buffer_length == 0 { /* Just connect bit reader to input stream. */
|
|
br.input_len = *available_in
|
|
br.input = *next_in
|
|
br.byte_pos = 0
|
|
} else {
|
|
/* At least one byte of input is required. More than one byte of input may
|
|
be required to complete the transaction -> reading more data must be
|
|
done in a loop -> do it in a main loop. */
|
|
result = decoderNeedsMoreInput
|
|
|
|
br.input = s.buffer.u8[:]
|
|
br.byte_pos = 0
|
|
}
|
|
|
|
/* State machine */
|
|
for {
|
|
if result != decoderSuccess {
|
|
/* Error, needs more input/output. */
|
|
if result == decoderNeedsMoreInput {
|
|
if s.ringbuffer != nil { /* Pro-actively push output. */
|
|
var intermediate_result int = writeRingBuffer(s, available_out, next_out, nil, true)
|
|
|
|
/* WriteRingBuffer checks s->meta_block_remaining_len validity. */
|
|
if int(intermediate_result) < 0 {
|
|
result = intermediate_result
|
|
break
|
|
}
|
|
}
|
|
|
|
if s.buffer_length != 0 { /* Used with internal buffer. */
|
|
if br.byte_pos == br.input_len {
|
|
/* Successfully finished read transaction.
|
|
Accumulator contains less than 8 bits, because internal buffer
|
|
is expanded byte-by-byte until it is enough to complete read. */
|
|
s.buffer_length = 0
|
|
|
|
/* Switch to input stream and restart. */
|
|
result = decoderSuccess
|
|
|
|
br.input_len = *available_in
|
|
br.input = *next_in
|
|
br.byte_pos = 0
|
|
continue
|
|
} else if *available_in != 0 {
|
|
/* Not enough data in buffer, but can take one more byte from
|
|
input stream. */
|
|
result = decoderSuccess
|
|
|
|
s.buffer.u8[s.buffer_length] = (*next_in)[0]
|
|
s.buffer_length++
|
|
br.input_len = uint(s.buffer_length)
|
|
*next_in = (*next_in)[1:]
|
|
(*available_in)--
|
|
|
|
/* Retry with more data in buffer. */
|
|
continue
|
|
}
|
|
|
|
/* Can't finish reading and no more input. */
|
|
break
|
|
/* Input stream doesn't contain enough input. */
|
|
} else {
|
|
/* Copy tail to internal buffer and return. */
|
|
*next_in = br.input[br.byte_pos:]
|
|
|
|
*available_in = br.input_len - br.byte_pos
|
|
for *available_in != 0 {
|
|
s.buffer.u8[s.buffer_length] = (*next_in)[0]
|
|
s.buffer_length++
|
|
*next_in = (*next_in)[1:]
|
|
(*available_in)--
|
|
}
|
|
|
|
break
|
|
}
|
|
}
|
|
|
|
/* Unreachable. */
|
|
|
|
/* Fail or needs more output. */
|
|
if s.buffer_length != 0 {
|
|
/* Just consumed the buffered input and produced some output. Otherwise
|
|
it would result in "needs more input". Reset internal buffer. */
|
|
s.buffer_length = 0
|
|
} else {
|
|
/* Using input stream in last iteration. When decoder switches to input
|
|
stream it has less than 8 bits in accumulator, so it is safe to
|
|
return unused accumulator bits there. */
|
|
bitReaderUnload(br)
|
|
|
|
*available_in = br.input_len - br.byte_pos
|
|
*next_in = br.input[br.byte_pos:]
|
|
}
|
|
|
|
break
|
|
}
|
|
|
|
switch s.state {
|
|
/* Prepare to the first read. */
|
|
case stateUninited:
|
|
if !warmupBitReader(br) {
|
|
result = decoderNeedsMoreInput
|
|
break
|
|
}
|
|
|
|
/* Decode window size. */
|
|
result = decodeWindowBits(s, br) /* Reads 1..8 bits. */
|
|
if result != decoderSuccess {
|
|
break
|
|
}
|
|
|
|
if s.large_window {
|
|
s.state = stateLargeWindowBits
|
|
break
|
|
}
|
|
|
|
s.state = stateInitialize
|
|
|
|
case stateLargeWindowBits:
|
|
if !safeReadBits(br, 6, &s.window_bits) {
|
|
result = decoderNeedsMoreInput
|
|
break
|
|
}
|
|
|
|
if s.window_bits < largeMinWbits || s.window_bits > largeMaxWbits {
|
|
result = decoderErrorFormatWindowBits
|
|
break
|
|
}
|
|
|
|
s.state = stateInitialize
|
|
fallthrough
|
|
|
|
/* Maximum distance, see section 9.1. of the spec. */
|
|
/* Fall through. */
|
|
case stateInitialize:
|
|
s.max_backward_distance = (1 << s.window_bits) - windowGap
|
|
|
|
/* Allocate memory for both block_type_trees and block_len_trees. */
|
|
s.block_type_trees = make([]huffmanCode, (3 * (huffmanMaxSize258 + huffmanMaxSize26)))
|
|
|
|
if s.block_type_trees == nil {
|
|
result = decoderErrorAllocBlockTypeTrees
|
|
break
|
|
}
|
|
|
|
s.block_len_trees = s.block_type_trees[3*huffmanMaxSize258:]
|
|
|
|
s.state = stateMetablockBegin
|
|
fallthrough
|
|
|
|
/* Fall through. */
|
|
case stateMetablockBegin:
|
|
decoderStateMetablockBegin(s)
|
|
|
|
s.state = stateMetablockHeader
|
|
fallthrough
|
|
|
|
/* Fall through. */
|
|
case stateMetablockHeader:
|
|
result = decodeMetaBlockLength(s, br)
|
|
/* Reads 2 - 31 bits. */
|
|
if result != decoderSuccess {
|
|
break
|
|
}
|
|
|
|
if s.is_metadata != 0 || s.is_uncompressed != 0 {
|
|
if !bitReaderJumpToByteBoundary(br) {
|
|
result = decoderErrorFormatPadding1
|
|
break
|
|
}
|
|
}
|
|
|
|
if s.is_metadata != 0 {
|
|
s.state = stateMetadata
|
|
break
|
|
}
|
|
|
|
if s.meta_block_remaining_len == 0 {
|
|
s.state = stateMetablockDone
|
|
break
|
|
}
|
|
|
|
calculateRingBufferSize(s)
|
|
if s.is_uncompressed != 0 {
|
|
s.state = stateUncompressed
|
|
break
|
|
}
|
|
|
|
s.loop_counter = 0
|
|
s.state = stateHuffmanCode0
|
|
|
|
case stateUncompressed:
|
|
result = copyUncompressedBlockToOutput(available_out, next_out, nil, s)
|
|
if result == decoderSuccess {
|
|
s.state = stateMetablockDone
|
|
}
|
|
|
|
case stateMetadata:
|
|
for ; s.meta_block_remaining_len > 0; s.meta_block_remaining_len-- {
|
|
var bits uint32
|
|
|
|
/* Read one byte and ignore it. */
|
|
if !safeReadBits(br, 8, &bits) {
|
|
result = decoderNeedsMoreInput
|
|
break
|
|
}
|
|
}
|
|
|
|
if result == decoderSuccess {
|
|
s.state = stateMetablockDone
|
|
}
|
|
|
|
case stateHuffmanCode0:
|
|
if s.loop_counter >= 3 {
|
|
s.state = stateMetablockHeader2
|
|
break
|
|
}
|
|
|
|
/* Reads 1..11 bits. */
|
|
result = decodeVarLenUint8(s, br, &s.num_block_types[s.loop_counter])
|
|
|
|
if result != decoderSuccess {
|
|
break
|
|
}
|
|
|
|
s.num_block_types[s.loop_counter]++
|
|
if s.num_block_types[s.loop_counter] < 2 {
|
|
s.loop_counter++
|
|
break
|
|
}
|
|
|
|
s.state = stateHuffmanCode1
|
|
fallthrough
|
|
|
|
case stateHuffmanCode1:
|
|
{
|
|
var alphabet_size uint32 = s.num_block_types[s.loop_counter] + 2
|
|
var tree_offset int = s.loop_counter * huffmanMaxSize258
|
|
result = readHuffmanCode(alphabet_size, alphabet_size, s.block_type_trees[tree_offset:], nil, s)
|
|
if result != decoderSuccess {
|
|
break
|
|
}
|
|
s.state = stateHuffmanCode2
|
|
}
|
|
fallthrough
|
|
|
|
case stateHuffmanCode2:
|
|
{
|
|
var alphabet_size uint32 = numBlockLenSymbols
|
|
var tree_offset int = s.loop_counter * huffmanMaxSize26
|
|
result = readHuffmanCode(alphabet_size, alphabet_size, s.block_len_trees[tree_offset:], nil, s)
|
|
if result != decoderSuccess {
|
|
break
|
|
}
|
|
s.state = stateHuffmanCode3
|
|
}
|
|
fallthrough
|
|
|
|
case stateHuffmanCode3:
|
|
var tree_offset int = s.loop_counter * huffmanMaxSize26
|
|
if !safeReadBlockLength(s, &s.block_length[s.loop_counter], s.block_len_trees[tree_offset:], br) {
|
|
result = decoderNeedsMoreInput
|
|
break
|
|
}
|
|
|
|
s.loop_counter++
|
|
s.state = stateHuffmanCode0
|
|
|
|
case stateMetablockHeader2:
|
|
{
|
|
var bits uint32
|
|
if !safeReadBits(br, 6, &bits) {
|
|
result = decoderNeedsMoreInput
|
|
break
|
|
}
|
|
|
|
s.distance_postfix_bits = bits & bitMask(2)
|
|
bits >>= 2
|
|
s.num_direct_distance_codes = numDistanceShortCodes + (bits << s.distance_postfix_bits)
|
|
s.distance_postfix_mask = int(bitMask(s.distance_postfix_bits))
|
|
s.context_modes = make([]byte, uint(s.num_block_types[0]))
|
|
if s.context_modes == nil {
|
|
result = decoderErrorAllocContextModes
|
|
break
|
|
}
|
|
|
|
s.loop_counter = 0
|
|
s.state = stateContextModes
|
|
}
|
|
fallthrough
|
|
|
|
case stateContextModes:
|
|
result = readContextModes(s)
|
|
|
|
if result != decoderSuccess {
|
|
break
|
|
}
|
|
|
|
s.state = stateContextMap1
|
|
fallthrough
|
|
|
|
case stateContextMap1:
|
|
result = decodeContextMap(s.num_block_types[0]<<literalContextBits, &s.num_literal_htrees, &s.context_map, s)
|
|
|
|
if result != decoderSuccess {
|
|
break
|
|
}
|
|
|
|
detectTrivialLiteralBlockTypes(s)
|
|
s.state = stateContextMap2
|
|
fallthrough
|
|
|
|
case stateContextMap2:
|
|
{
|
|
var num_direct_codes uint32 = s.num_direct_distance_codes - numDistanceShortCodes
|
|
var num_distance_codes uint32
|
|
var max_distance_symbol uint32
|
|
if s.large_window {
|
|
num_distance_codes = uint32(distanceAlphabetSize(uint(s.distance_postfix_bits), uint(num_direct_codes), largeMaxDistanceBits))
|
|
max_distance_symbol = maxDistanceSymbol(num_direct_codes, s.distance_postfix_bits)
|
|
} else {
|
|
num_distance_codes = uint32(distanceAlphabetSize(uint(s.distance_postfix_bits), uint(num_direct_codes), maxDistanceBits))
|
|
max_distance_symbol = num_distance_codes
|
|
}
|
|
var allocation_success bool = true
|
|
result = decodeContextMap(s.num_block_types[2]<<distanceContextBits, &s.num_dist_htrees, &s.dist_context_map, s)
|
|
if result != decoderSuccess {
|
|
break
|
|
}
|
|
|
|
if !decoderHuffmanTreeGroupInit(s, &s.literal_hgroup, numLiteralSymbols, numLiteralSymbols, s.num_literal_htrees) {
|
|
allocation_success = false
|
|
}
|
|
|
|
if !decoderHuffmanTreeGroupInit(s, &s.insert_copy_hgroup, numCommandSymbols, numCommandSymbols, s.num_block_types[1]) {
|
|
allocation_success = false
|
|
}
|
|
|
|
if !decoderHuffmanTreeGroupInit(s, &s.distance_hgroup, num_distance_codes, max_distance_symbol, s.num_dist_htrees) {
|
|
allocation_success = false
|
|
}
|
|
|
|
if !allocation_success {
|
|
return saveErrorCode(s, decoderErrorAllocTreeGroups)
|
|
}
|
|
|
|
s.loop_counter = 0
|
|
s.state = stateTreeGroup
|
|
}
|
|
fallthrough
|
|
|
|
case stateTreeGroup:
|
|
var hgroup *huffmanTreeGroup = nil
|
|
switch s.loop_counter {
|
|
case 0:
|
|
hgroup = &s.literal_hgroup
|
|
case 1:
|
|
hgroup = &s.insert_copy_hgroup
|
|
case 2:
|
|
hgroup = &s.distance_hgroup
|
|
default:
|
|
return saveErrorCode(s, decoderErrorUnreachable)
|
|
}
|
|
|
|
result = huffmanTreeGroupDecode(hgroup, s)
|
|
if result != decoderSuccess {
|
|
break
|
|
}
|
|
s.loop_counter++
|
|
if s.loop_counter >= 3 {
|
|
prepareLiteralDecoding(s)
|
|
s.dist_context_map_slice = s.dist_context_map
|
|
s.htree_command = []huffmanCode(s.insert_copy_hgroup.htrees[0])
|
|
if !ensureRingBuffer(s) {
|
|
result = decoderErrorAllocRingBuffer2
|
|
break
|
|
}
|
|
|
|
s.state = stateCommandBegin
|
|
}
|
|
|
|
case stateCommandBegin, stateCommandInner, stateCommandPostDecodeLiterals, stateCommandPostWrapCopy:
|
|
result = processCommands(s)
|
|
|
|
if result == decoderNeedsMoreInput {
|
|
result = safeProcessCommands(s)
|
|
}
|
|
|
|
case stateCommandInnerWrite, stateCommandPostWrite1, stateCommandPostWrite2:
|
|
result = writeRingBuffer(s, available_out, next_out, nil, false)
|
|
|
|
if result != decoderSuccess {
|
|
break
|
|
}
|
|
|
|
wrapRingBuffer(s)
|
|
if s.ringbuffer_size == 1<<s.window_bits {
|
|
s.max_distance = s.max_backward_distance
|
|
}
|
|
|
|
if s.state == stateCommandPostWrite1 {
|
|
if s.meta_block_remaining_len == 0 {
|
|
/* Next metablock, if any. */
|
|
s.state = stateMetablockDone
|
|
} else {
|
|
s.state = stateCommandBegin
|
|
}
|
|
|
|
break
|
|
} else if s.state == stateCommandPostWrite2 {
|
|
s.state = stateCommandPostWrapCopy /* BROTLI_STATE_COMMAND_INNER_WRITE */
|
|
} else {
|
|
if s.loop_counter == 0 {
|
|
if s.meta_block_remaining_len == 0 {
|
|
s.state = stateMetablockDone
|
|
} else {
|
|
s.state = stateCommandPostDecodeLiterals
|
|
}
|
|
|
|
break
|
|
}
|
|
|
|
s.state = stateCommandInner
|
|
}
|
|
|
|
case stateMetablockDone:
|
|
if s.meta_block_remaining_len < 0 {
|
|
result = decoderErrorFormatBlockLength2
|
|
break
|
|
}
|
|
|
|
decoderStateCleanupAfterMetablock(s)
|
|
if s.is_last_metablock == 0 {
|
|
s.state = stateMetablockBegin
|
|
break
|
|
}
|
|
|
|
if !bitReaderJumpToByteBoundary(br) {
|
|
result = decoderErrorFormatPadding2
|
|
break
|
|
}
|
|
|
|
if s.buffer_length == 0 {
|
|
bitReaderUnload(br)
|
|
*available_in = br.input_len - br.byte_pos
|
|
*next_in = br.input[br.byte_pos:]
|
|
}
|
|
|
|
s.state = stateDone
|
|
fallthrough
|
|
|
|
case stateDone:
|
|
if s.ringbuffer != nil {
|
|
result = writeRingBuffer(s, available_out, next_out, nil, true)
|
|
if result != decoderSuccess {
|
|
break
|
|
}
|
|
}
|
|
|
|
return saveErrorCode(s, result)
|
|
}
|
|
}
|
|
|
|
return saveErrorCode(s, result)
|
|
}
|
|
|
|
func decoderHasMoreOutput(s *Reader) bool {
|
|
/* After unrecoverable error remaining output is considered nonsensical. */
|
|
if int(s.error_code) < 0 {
|
|
return false
|
|
}
|
|
|
|
return s.ringbuffer != nil && unwrittenBytes(s, false) != 0
|
|
}
|
|
|
|
func decoderGetErrorCode(s *Reader) int {
|
|
return int(s.error_code)
|
|
}
|
|
|
|
func decoderErrorString(c int) string {
|
|
switch c {
|
|
case decoderNoError:
|
|
return "NO_ERROR"
|
|
case decoderSuccess:
|
|
return "SUCCESS"
|
|
case decoderNeedsMoreInput:
|
|
return "NEEDS_MORE_INPUT"
|
|
case decoderNeedsMoreOutput:
|
|
return "NEEDS_MORE_OUTPUT"
|
|
case decoderErrorFormatExuberantNibble:
|
|
return "EXUBERANT_NIBBLE"
|
|
case decoderErrorFormatReserved:
|
|
return "RESERVED"
|
|
case decoderErrorFormatExuberantMetaNibble:
|
|
return "EXUBERANT_META_NIBBLE"
|
|
case decoderErrorFormatSimpleHuffmanAlphabet:
|
|
return "SIMPLE_HUFFMAN_ALPHABET"
|
|
case decoderErrorFormatSimpleHuffmanSame:
|
|
return "SIMPLE_HUFFMAN_SAME"
|
|
case decoderErrorFormatClSpace:
|
|
return "CL_SPACE"
|
|
case decoderErrorFormatHuffmanSpace:
|
|
return "HUFFMAN_SPACE"
|
|
case decoderErrorFormatContextMapRepeat:
|
|
return "CONTEXT_MAP_REPEAT"
|
|
case decoderErrorFormatBlockLength1:
|
|
return "BLOCK_LENGTH_1"
|
|
case decoderErrorFormatBlockLength2:
|
|
return "BLOCK_LENGTH_2"
|
|
case decoderErrorFormatTransform:
|
|
return "TRANSFORM"
|
|
case decoderErrorFormatDictionary:
|
|
return "DICTIONARY"
|
|
case decoderErrorFormatWindowBits:
|
|
return "WINDOW_BITS"
|
|
case decoderErrorFormatPadding1:
|
|
return "PADDING_1"
|
|
case decoderErrorFormatPadding2:
|
|
return "PADDING_2"
|
|
case decoderErrorFormatDistance:
|
|
return "DISTANCE"
|
|
case decoderErrorDictionaryNotSet:
|
|
return "DICTIONARY_NOT_SET"
|
|
case decoderErrorInvalidArguments:
|
|
return "INVALID_ARGUMENTS"
|
|
case decoderErrorAllocContextModes:
|
|
return "CONTEXT_MODES"
|
|
case decoderErrorAllocTreeGroups:
|
|
return "TREE_GROUPS"
|
|
case decoderErrorAllocContextMap:
|
|
return "CONTEXT_MAP"
|
|
case decoderErrorAllocRingBuffer1:
|
|
return "RING_BUFFER_1"
|
|
case decoderErrorAllocRingBuffer2:
|
|
return "RING_BUFFER_2"
|
|
case decoderErrorAllocBlockTypeTrees:
|
|
return "BLOCK_TYPE_TREES"
|
|
case decoderErrorUnreachable:
|
|
return "UNREACHABLE"
|
|
default:
|
|
return "INVALID"
|
|
}
|
|
}
|
|
|